The present invention concerns a novel industrial method of treating oil sand.
Oil sand is a substance attracting notice as the next energy source in place of crude petroleum oil. It is composed of particles 0.05-2.0 mm in diameter of silica sand having their surface covered by a mixture of heavy hydrocarbons called bitumen having a boiling point of higher than 200.degree. C. and specific gravity corresponding to API 8-16. The oil sand containing hydrocarbons more than 10% by weight of itself is said to be profitable from the view point of natural resources.
The economical disadvantages of oil sand consist in a large amount of energy necessary for separating bitumen from silica sand and the difficulty of transportation of the separated bitumen due to its heaviness and viscousness. Especially, considering the environmental situation of the producing district of oil sand, it is very difficult to transport the bitumen for the purpose of rectification. Because the zones of deposition of oil sand situate in the inland area of undeveloped lands where the facilities of energy for development are not sufficient. Also, in order to collect the oil sand bitumen, a method of extraction with hot water of oil sand excavated by open-air mining or a method of collecting bitumen by pumps after fluidizing the oil sand by supplying directly the energy to the deposit of oil sand is adopted, and it is estimated that an amount of energy corresponding to about 20% of the oil sand bitumen calculated as a fuel is necessary for collecting the oil sand bitumen. The collected oil sand-bitumen itself is highly viscous as it is and its high viscosity makes its transportation very difficult.
In prior art, the collected bitumen is at first subjected to a distillation and then the residue of distillation is subjected to the so-called coking procedure to be converted into the distillable products such as naphtha, kerosene, gas oil, etc. and coke. As a typical one, two types of coking procedures are known in the art, they being:
(1) Delayed coking. This proceeds in two stages; the bitumen is rapidly heated in a feed furnace, and then resides for a time in coke drums where the large bitumen molecules are cracked into smaller ones, thus forming distillable products: naphtha, kerosene and gas oil. PA1 (2) Fluid coking. The coker reactor contains fine coke particles in rapid motion in a gas ("fluid" coke) at about 500.degree. C. into which bitumen and steam are fed. The bitumen vaporizes and cracks on contact with the coke and the products are fed to downstream processing. (from T. Williams; Science Affairs, 1976, Vol. 9, No. 3, pages 15-18).
However, not only are these procedures very complicated in their procedures but also the effectiveness of the produced coke as a source of thermal energy is not necessarily high enough.
Accordingly, the main object of the present invention is to make an offer of an economical process of oil sand treating process which supplies a large amount of energy within its process effectively and by which heavy bitumens are converted to oils suitable for transportation.